Am I overbuilding This Cob Light??

[Sxott]

Thanks to our Greedy legislators up here in WA, Medical patients plant counts and limits just got slammed to eliminate "competition" with the heavy taxed recreational market. Now I have to make do with much less plants.

Im currently converting a 1000 Watt HPS into 2x 2x4x42"h COB cabinets and will be scrogging in it with lights 10-12" above canopy. (too close?)

I have already ordered parts for these cabinets:

CAB 1) 10x cxb3070 AD ~ 2x HLG-185-1050C = 60740 Lumens @ @ 365 watts
CAB 2) 8x cbx3590 CB ~ 2x HLG-185-1400C (have not bought drivers yet) = 65600 Lumens @ 390 Watts
All 3000k. I also have all my other parts or them on the way. Thats about 25% less light than my HPS and minus the AC too.

Is this an overkill for these 2x4 cabinets? I see people on here using little as 200 COB watts in a 2x4 cabinet but, I dont see many journals showing their performance and final weights. Im hoping for about 12 zips or more per cabinet. I can get that in the same space with 500 watts of HPS. I just dont want to be wasting juice and build money if I will not benefit from it.

What kind of weights are you guys getting and your space / methods using these COBs?

 

[youngbotanist355]

https://www.rollitup.org/t/cob-efficiency-spreadsheets.865238/
Use this to find the efficiency of your diodes at the current you chose and multiply that percentage by your total watt draw to get your par watts and you want to have around 15-20 par watts per square foot of grow space. Just by a quick figure in my head you are at around 22-25 par watts per square foot which isn't overkill but you reach a point of diminishing returns after a certain point so you could reduce it a little bit without a substantial loss in yield

 

[churchhaze]

I'd call 22-25W/sqft PAR overkill unless it was 7+ foot tall plants. I do good with 12W/sqft of PAR with 2-3ft plants.

 

[Sxott]

Thanks guys.
I did not know exactly how to calculate the par watts on them sheets work until now.

More question now: Since "PAR" is 400 and 700 nanometers and the blue and reds sides of it are the most important. Wouldn't the quality of the "PAR" vary per spectrum? Because green, yellow and, orange is considered PAR also right? Church - Is this the reason you are saying 12w/sqft will work? Are White LEDs that much more quality of a spectrum than HPS? Because I figured HPS puts out about 22.5 par watts a square foot (but has tons of yellow). Or is it that with COBS we can spread it out and get em closer? Both?

Another light I was thinking about making would be a 2700k / 5000k 60/40 combination light. The 2700K to be switched on after vegging. This would save juice in veg without needing a second light for the blues (vegging) . Would it be much more beneficial to dedicate the whole flowering wattage to the red side of things for flower or the combo to be the way to go? I could minimize the "PAR" that gets used the least making a lower PAr/watt a better quality?

 

[youngbotanist355]

You can actually just wire in a 50k dimmer on the b version of the hgl drivers and dim the whole fixture down to 10% if you want and just run 3000k for veg too the cxbs have enough blue even at 3000k to do so

 

[youngbotanist355]

50k for 2 drivers. It's 100/n where n is the number of drivers

 

[Sxott]

That is awesome because I was thinking I missed out by getting the B version instead of the A. Can you point me to some good ones?

 

[Alienwidow]

What do you mean WA just got slammed?

 

[Rahz]

I'm running 350 watts output of V29s @ .7A for about 50,000 lumens in just over 2x4' (10 cubic foot) space and have gotten 1.35 GPW by output so far. 1.7 zips per square foot.

What you're doing seems perfectly reasonable if there are space/plant constraints. I'm working on a 200 watt 30,000 lumen lamp that I will sub in after this next run, so I will have an interesting point of comparison. I would love to hit 1.5 GPW with it but the raw power of the first lamp will very likely win the overall yield. I will tell you that you will most certainly get more than 12 zips per cabinet.

Such intensities for veg would be overkill, but for flower maybe not... although I have to say the veg under my v29 lamp could be characterized as Xtreme.

 

[Sxott]

Rivers Bill 5052 just passed yesterday. All its waiting on now is that crooked ass Jay Inslee to sign it.

We all just got fucked over by the "Patient Protection Act" Its funny because it should have benn called "Destroy MMJ Act"
What is was is that they seen MMJ as a threat to thier potential recreation market revenue and tax money prevailed over the peoples will and basic patients rights.

 

[Sxott]

I'm running 350 watts output of V29s @ .7A for about 50,000 lumens in just over 2x4' (10 cubic foot) space and have gotten 1.35 GPW by output so far. 1.7 zips per square foot.

What you're doing seems perfectly reasonable if there are space/plant constraints. I'm working on a 200 watt 30,000 lumen lamp that I will sub in after this next run, so I will have an interesting point of comparison. I would love to hit 1.5 GPW with it but the raw power of the first lamp will very likely win the overall yield. I will tell you that you will most certainly get more than 12 zips per cabinet.

Such intensities for veg would be overkill, but for flower maybe not... although I have to say the veg under my v29 lamp could be characterized as Xtreme.

Thats what I want to hear Thanks. The combo light I been planning in my head is with Vero 18s. Looking forward to your results.

I was thinking 200 watts of veg. 100 watts in the middle when its small and flip another 100 on when its hits the screen. Then then the rest come flower time. I need a plant to go from clone to ready to flip on the screen in the time it takes one in a flower cabinet to finish (8-9 weeks) so I can keep a constant cycle with no down time and no mammas. If I can get them even bigger in veg, I will have to sell my cabinets and build bigger ones.

 

[SupraSPL]

Thanks guys.
I did not know exactly how to calculate the par watts on them sheets work until now.

More question now: Since "PAR" is 400 and 700 nanometers and the blue and reds sides of it are the most important. Wouldn't the quality of the "PAR" vary per spectrum? Because green, yellow and, orange is considered PAR also right? Church - Is this the reason you are saying 12w/sqft will work? Are White LEDs that much more quality of a spectrum than HPS? Because I figured HPS puts out about 22.5 par watts a square foot (but has tons of yellow). Or is it that with COBS we can spread it out and get em closer? Both?

Good score on those COBs man. You are correct, the wider spectrum will change the efficacy of the PAR W and the photon count. Even more important is the difference in terms of reflector losses and spread. Reduced heat, infrared and electric bill will be a nice bonus. I think 1gpw it is a safe goal and potentially much higher.

For your CXB3070 setup:
365 (dissipation W) * .5128 (COB efficiency) = 187 PAR W
187 PAR W/8 ft² = 23.4 PAR W/ft²
23.4 * 10.7 (ft² in 1 m²) = 250 PAR W/m²
250 * 4.88 (umol/PAR W for CXA 3000K) = 1220 PPFD. (minus small % for lateral and upward scatter)

So 1200 PPFD is your average photon count, extrapolated to 1 m². That is very high intensity, which suffers from the law of diminishing returns when you get above 600-800. That is especially true when the PPFD has hot spots. So Church recommended spreading that light out which will significantly increase your efficiency and your yield. BUT if you are limited to that space, might as well rock it

 

[Sxott]

Good score on those COBs man. You are correct, the wider spectrum will change the efficacy of the PAR W and the photon count. Even more important is the difference in terms of reflector losses and spread. Reduced heat, infrared and electric bill will be a nice bonus. I think 1gpw it is a safe goal and potentially much higher.

For your CXB3070 setup:
365 (dissipation W) * .5128 (COB efficiency) = 187 PAR W
187 PAR W/8 ft² = 23.4 PAR W/ft²
23.4 * 10.7 (ft² in 1 m²) = 250 PAR W/m²
250 * 4.88 (umol/PAR W for CXA 3000K) = 1220 PPFD. (minus small % for lateral and upward scatter)

So 1200 PPFD is your average photon count, extrapolated to 1 m². That is very high intensity, which suffers from the law of diminishing returns when you get above 600-800. That is especially true when the PPFD has hot spots. So Church recommended spreading that light out which will significantly increase your efficiency and your yield. BUT if you are limited to that space, might as well rock it

View attachment 3393657

Thanks for the knowledge. Here and in all the other posts / sheets I have been reading.

 

[SupraSPL]

Glad if we can help a fellow DIYer. Also to respond to your comment "I figured HPS puts out about 22.5 par watts a square foot". The 1000HPS in a 4X4:

1000 (dissipation W) * .36 (HPS efficiency average over 12-18 mnths) = 360 PAR W
Apply 20% reflector losses (288 PAR W) and 10% glass losses (260 PAR W)
260 PAR W/16 ft² = 16.2 PAR W/ft²
16.2 * 10.7 (ft² in 1 m²) = 173 PAR W/m²
173 * 4.98 (umol/PAR W for HPS) = 863 PPFD

So 863 is the average intensity but likely there would be much higher intensity in the center of the 4X4 and much less at the edges. The COBs will reduce that gradient to some extent.

863 vs 1200 PPFD, I think this explains the phenomenon of nute deficiencies when growing with COBs versus HPS, the plants are hungry and a hungry plant can show a wide variety of symptoms that can have growers chasing their tails. This is especially noticeable if you switch from a dim vegging area to a bright flowering area.

 

[Sxott]

I never took the losses in to consideration. Your getting me all excited now. Im itching to get these built. I have been constantly hitting the refresh button on the tracking pages. They move so much slower that way. haha

 

[Mellodrama]

Supra -
Don't you ever leave. You're stuck here now. We all depend on you to show up with all those calculations that nobody else knows how to figure out.

Well, I don't anyway.

 

[Sxott]

I dont know where the 4.98 and 4.88 numbers come from (umol/PAR W) ? Is there some references out there on all the common COBs that I can use to figure out ppfd? I dont see them on your spreadsheets.

 

[Sxott]

I found this goverment study on Canabis. It says 1500 is idea ppfd. Is there a reason you say 600-800? Too little gain for that much more juice?

http://www.ncbi.nlm.nih.gov/pubmed/23572895

Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions.

Effect of different photosynthetic photon flux densities (0, 500, 1000, 1500 and 2000 μmol m(-2)s(-1)), temperatures (20, 25, 30, 35 and 40 °C) and CO2 concentrations (250, 350, 450, 550, 650 and 750 μmol mol(-1)) on gas and water vapour exchange characteristics of Cannabis sativa L. were studied to determine the suitable and efficient environmental conditions for its indoor mass cultivation for pharmaceutical uses. The rate of photosynthesis (PN) and water use efficiency (WUE) of Cannabis sativa increased with photosynthetic photon flux densities (PPFD) at the lower temperatures (20-25 °C). At 30 °C, PN and WUE increased only up to 1500 μmol m(-2)s(-1) PPFD and decreased at higher light levels. The maximum rate of photosynthesis (PN max) was observed at 30 °C and under 1500 μmol m(-2)s(-1) PPFD. The rate of transpiration (E) responded positively to increased PPFD and temperature up to the highest levels tested (2000 μmol m(-2)s(-1) and 40 °C). Similar to E, leaf stomatal conductance (gs) also increased with PPFD irrespective of temperature. However, gs increased with temperature up to 30 °C only. Temperature above 30 °C had an adverse effect on gs in this species. Overall, high temperature and high PPFD showed an adverse effect on PN and WUE. A continuous decrease in intercellular CO2 concentration (Ci) and therefore, in the ratio of intercellular CO2 to ambient CO2 concentration (Ci/Ca) was observed with the increase in temperature and PPFD. However, the decrease was less pronounced at light intensities above 1500 μmol m(-2)s(-1). In view of these results, temperature and light optima for photosynthesis was concluded to be at 25-30 °C and ∼1500 μmol m(-2)s(-1) respectively. Furthermore, plants were also exposed to different concentrations of CO2 (250, 350, 450, 550, 650 and 750 μmol mol(-1)) under optimum PPFD and temperature conditions to assess their photosynthetic response. Rate of photosynthesis, WUE and Ci decreased by 50 %, 53 % and 10 % respectively, and Ci/Ca, E and gs increased by 25 %, 7 % and 3 % respectively when measurements were made at 250 μmol mol-1 as compared to ambient CO2 (350 μmol mol(-1)) level. Elevated CO2 concentration (750 μmol mol(-1)) suppressed E and gs ∼ 29% and 42% respectively, and stimulated PN, WUE and Ci by 50 %, 111 % and 115 % respectively as compared to ambient CO2 concentration. The study reveals that this species can be efficiently cultivated in the range of 25 to 30 °C and ∼1500 μmol m(-2)s(-1) PPFD. Furthermore, higher PN, WUE and nearly constant Ci/Ca ratio under elevated CO2 concentrations in C. sativa, reflects its potential for better survival, growth and productivity in drier and CO2 rich environment.

 

[SupraSPL]

I dont know where the 4.98 and 4.88 numbers come from (umol/PAR W) ? Is there some references out there on all the common COBs that I can use to figure out ppfd? I dont see them on your spread sheets.

Those numbers were calculated from the SPD curves thanks to the hard work of @alesh and @MrFlux


I have not included that data in the spreadsheets but it may be a good idea to add a umol/s/W column.

 

[SupraSPL]

The paper discovered "maximum rate of photosynthesis (PN max) was observed at 30 °C and under 1500 μmol m(-2)s(-1) PPFD"

But they conclude "In view of these results, temperature and light optima for photosynthesis was concluded to be at 25-30 °C and ∼1500 μmol m(-2)s(-1) respectively"

Their data is consistent with most PPFD charts I have seen. But they made a mental leap there from "max" to "optimal". You are correct the reason (KNNA) recommended lower than 1500 as "optimal" for indoor growing is based on efficiency. If your average PPFD is at 1500, that means there are likely bright spots that are above 1500. Also may results in significant heat in the canopy from infrared radiation and photon conversion that is going to be electrically expensive to get rid of. But, if your space is highly limited, you can aim for 1500 and potentially increase the yield.